The conventional steel industry process for fulfilling a customer's order for a steel product with particular mechanical, dimensional and finish properties is complicated and time-consuming, and may typically require 10 or more weeks to accomplish. Referring to FIG. 1, for example, a flowchart is shown illustrating a flow of one conventional process 10 for producing a customer-ordered steel strip product, wherein the term “strip” as used herein is to be understood to mean a product of 5 mm thickness or less.
Process 10 begins at step 12 where the steel manufacturer receives the customer order, typically set forth in terms of mechanical (e.g., yield strength), dimensional and finish requirements for the steel strip product as well as a desired quantity. Thereafter at step 14, the steel manufacturer determines from the customer order the particular steel chemistry requirements for achieving the product's specified properties. The chemistry requirements are selected from a large recipe list of steel chemistries that is available (and in many cases dates back to ingot casting/hot rolling technology where chemistry was the prime determinant of mechanical and finish properties). Thereafter at step 16, the steel manufacturer determines casting parameters corresponding to operating parameters and/or set points for a steel casting process that will be used to produce steel slabs from molten steel formed in accordance with the steel chemistry requirements. At step 18, the steel manufacturer determines downstream slab processing requirements, initially focusing on achieving the customer's dimensional requirements such as thickness etc and then working through additional downstream processing steps that may be required to achieve the final product properties. Such downstream slab processing requirements may include, for example, any one or combination of (a) slab reheat parameters corresponding to hot mill furnace operating parameters and/or set points for hot strip mill processing, (b) hot rolling parameters corresponding to mill rolling operating parameters and/or set points for hot strip mill processing, (c) cold rolling parameters corresponding to pickling and cold rolling operating parameters and/or set points for cold mill processing, and (d) heat treatment parameters corresponding to heat treatment operating parameters and/or set points for heat treatment.
From step 18, process 10 advances to step 20 where the steel manufacturer produces a batch of molten steel in accordance with the chemistry requirements for the specified steel product and casts the steel product into slab stock in accordance with the casting parameters established at step 16. Oftentimes, customer's orders (which can be as small as 5 tonnes) are batched together until there are sufficient orders to fill one steelmaking heat—typically 100 to 300 tonnes depending on the specific steel plant capacity. This adds further delay to the time that a particular customer's order can be filled, thereby extending the total time for production well in excess of 10 weeks. In any case, process 10 advances from step 20 to step 22 where the slab stock is reheated and hot rolled at hot strip mill, in accordance with the slab reheat and hot rolling parameters established at step 18, to produce steel coil stock of a predefined thickness. Thereafter at step 24, the coil stock is pickled and cold rolled at a cold mill in accordance with any pickling and cold rolling parameters established at step 18 to reduce the thickness of the coil stock to a customer-specified thickness and also to achieve desired properties. Finally, at step 26 the coil stock is heat treated in accordance with any heat treatment parameters established at step 18 to anneal the coil stock such that it meets the requirements of the customer's order.
Conventional steel strip production of the type just described necessitates the production of many different steel grades (typically, in excess of 50) that are first cast into slabs and then processed through complex hot rolling schedules in hot strip mills that produce product in thicknesses as low as 1.5 mm with yield strengths generally in the range 300 to 450 MPa. If the customer requires thinner material or properties outside this range, subsequent processing involving pickle lines, cold reduction mills and annealing furnaces is required.
A primary drawback associated with the conventional steel strip production process just described is the lengthy time period; typically 10 or more weeks, required to produce the steel product that satisfies the customer order. What is therefore needed is an improved steel strip production process that is more responsive to customer needs by greatly reducing the time required to produce customer-specified steel strip product.